Electronic industrial wastewater deep defluorination composite coagulant based on pH self-adaption and stage treatment method

Abstract

The invention provides an electronic industrial wastewater deep defluorination composite coagulant based on pH self-adaption and a stage treatment method, and belongs to the technical field of industrial wastewater deep treatment. The composite coagulant is formed by compounding aluminum sulfate and polyaluminum chloride according to the mass ratio of (1: 3)-(3: 1), self-adaptive pH regulation and control are achieved through a two-component synergistic hydrolysis equilibrium mechanism, an aluminum salt form complementation and synergism mechanism is combined, a dynamic proportion adjustment technology is supplemented, the component proportion can be flexibly adjusted according to water quality fluctuation, a first-stage / second-stage stage treatment process is matched, and the composite coagulant has the advantages of high water quality and high water quality. And deep removal of fluorine ions is realized in stages. The method breaks through the dependence of the traditional process on stable water quality, obviously reduces the acid-base consumption and sludge treatment cost, and has the obvious advantages of high efficiency, economy and easiness in popularization.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced treatment of industrial wastewater, and particularly relates to a composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH self - adaptation and a hierarchical treatment method. Background Technique

[0002] Fluoride is a trace element required by the human body, and it has a double - threshold effect. The appropriate fluoride concentration in drinking water is 0.5 - 1.0 mg / L. Long - term drinking of fluoride - containing water with a concentration exceeding 1.0 mg / L will cause diseases such as dental fluorosis and skeletal fluorosis. In recent years, the electronic industry has developed vigorously, and the amount of fluoride - containing wastewater generated has increased sharply, discharging a large amount of fluoride into the surrounding environment every year. As one of the characteristic pollutants in electronic industrial wastewater, fluoride mainly comes from ammonium fluoride and hydrofluoric acid widely used in the etching process. The concentration of fluoride - containing wastewater generated by electronic - related enterprises is generally several hundred to several thousand milligrams per liter, and generally, it is treated to below the industry discharge standard of 10 - 20 mg / L by chemical precipitation or chemical - coagulation precipitation. Deep fluoride removal has become a new challenge in the field of industrial wastewater treatment, and it is necessary to carry out research on deep fluoride removal of low - concentration fluoride - containing wastewater. Currently, the main deep fluoride - removal processes include chemical precipitation, adsorption, electrochemistry, ion exchange, coagulation precipitation, and hybrid processes of these methods.

[0003] The coagulation precipitation method has obvious advantages both in terms of project investment and operating cost, and its operation and maintenance are relatively simple. In addition, due to the maturity of relevant supporting structures and facilities, etc., for improving the fluoride ion standard of the effluent, the coagulation precipitation method can make the best use of the original process structures. Therefore, as a most cost - effective deep fluoride - removal process, coagulation precipitation has broad application and development prospects.

[0004] Although the coagulation precipitation process has many advantages in fluoride removal compared with other processes, using traditional coagulants for deep fluoride removal also faces some bottleneck problems such as large dosage of chemicals and high sludge treatment and disposal costs. Taking aluminum sulfate as an example of traditional coagulants, its fluoride - removal effect is good, but due to its strong hydrolysis effect, adding it to wastewater will cause a large - amplitude decrease in the pH value of the wastewater. In order to maintain the optimal pH for the fluoride - removal reaction, a large amount of alkali needs to be consumed, and the use cost is high. Polyaluminum chloride (PAC) is also a commonly used coagulant in deep fluoride removal. However, compared with aluminum sulfate, its fluoride - removal effect is relatively poor, but its hydrolysis degree is relatively weak. At the same dosing concentration, after adding it to the reaction system, the pH of the system will not drop significantly. In view of this, the present invention provides a composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH self - adaptation and a hierarchical treatment method. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a pH - adaptive composite coagulant for deep fluoride removal from electronic industrial wastewater and a hierarchical treatment method. Using the composite coagulant provided by the present invention can achieve a better deep fluoride removal effect on the basis of saving the costs of acids, alkalis, and coagulants.

[0006] To achieve the above object, the present invention provides a pH - adaptive composite coagulant for deep fluoride removal from electronic industrial wastewater, which is composed of an inorganic small - molecule coagulant and an inorganic polymer coagulant with a mass ratio of (1∶3)~(3∶1). The inorganic small - molecule coagulant is aluminum sulfate, and the inorganic polymer coagulant is polyaluminum chloride (PAC).

[0007] A pH - adaptive composite coagulant for deep fluoride removal from electronic industrial wastewater in the present invention is formed by mixing aluminum sulfate and polyaluminum chloride (PAC) with a mass ratio of (1∶3)~(3∶1). The composition of the composite coagulant determines the fluoride removal effect of electronic industrial wastewater. During the fluoride removal process, by controlling the dosage ratio of aluminum sulfate and polyaluminum chloride in the composite coagulant, the pH of the fluoride - containing wastewater is maintained at 6.5±0.2 without adding or adding a small amount of exogenous acids and alkalis. Under the above conditions, Al 3+ is more likely to convert dissolved aluminum into particulate aluminum (Al(OH)3). As the content of Al(OH)3 increases, the pH increases, thereby increasing the basicity of PAC and making it easier to combine with electronegative F - to further remove fluoride ions in water. Therefore, compared with a single fluoride - removal agent, the present invention combines two aluminum salts and utilizes their pH adaptability to achieve a more excellent fluoride - removal effect. And compared with existing composite coagulants (such as the patent with application number CN202410519445.4), the composite coagulant of the present invention has easily available raw materials, a simple preparation method, and is more economically beneficial, suitable for large - scale popularization and production.

[0008] The composite coagulant of the present invention has the characteristic of "pH - adaptive design", which is mainly achieved through the following mechanism:

[0009] 1. Two - component synergistic hydrolysis equilibrium mechanism

[0010] Aluminum sulfate (Al2(SO4)3), as a small - molecule coagulant, releases a large amount of Al 3+ and H + during hydrolysis (reaction formula: Al 3+ +3H2O→Al(OH)3↓+3H + ), significantly reducing the pH of the system; while polyaluminum chloride (PAC), as a polymer coagulant, has a relatively low hydrolysis degree of its pre - polymerized aluminum salt structure and releases H +The speed and quantity are milder. After the two are compounded in a ratio of (1:3) to (3:1), the strong hydrolysis of aluminum sulfate and the weak hydrolysis of PAC form a dynamic equilibrium:

[0011] When the initial wastewater pH is relatively high (such as 7 - 9), aluminum sulfate dominates the release of H + , neutralizes the OH in the wastewater - , and quickly reduces the pH to the optimal range (6.5 ± 0.2);

[0012] When the initial pH is close to neutral, the buffering effect of PAC can inhibit the excessive decrease of pH and reduce the demand for acid-base regulators.

[0013] 2. Complementary and synergistic effects of aluminum salt forms

[0014] The Al generated by the hydrolysis of aluminum sulfate 3+ forms Al(OH)3 colloid through complexation and directly adsorbs F - ; while the polymer chain of PAC connects the Al(OH)3 colloid into a dense floc through "bridging" action, enhancing the net trapping ability for F - . The synergistic effect of the two not only improves the defluorination efficiency but also stabilizes the pH by adjusting the Al 3+ release rate.

[0015] 3. Dynamic pH feedback regulation

[0016] After the composite coagulant is added, the ratio of aluminum sulfate to PAC can be dynamically adjusted according to the initial pH of the wastewater and the F - concentration. For example:

[0017] If the initial pH is relatively high (>7.5), increase the proportion of aluminum sulfate to enhance the release of H + , and quickly reduce the pH;

[0018] If the initial pH is close to neutral (6.5 - 7.5), increase the proportion of PAC to maintain pH stability.

[0019] This ratio flexibility (1:3 - 3:1) enables the composite coagulant to adapt to different water quality conditions.

[0020] 4. Optimization of sludge structure to reduce interference

[0021] The flocs generated by the composite coagulant are denser, and the sedimentation performance is better than that of a single agent. The dense flocs reduce the interference of residual Al(OH)3 on subsequent reactions, avoid pH fluctuations caused by loose flocs, and further strengthen pH stability.

[0022] The present invention also provides a preparation method of the pH self-adaptive deep defluorination composite coagulant for electronic industrial wastewater as described above, including the following steps:

[0023] Weigh each raw material according to the mass ratio, dissolve aluminum sulfate in water and stir evenly, and then add polyaluminum chloride. After stirring evenly, the pH self-adaptive deep defluorination composite coagulant for electronic industrial wastewater is obtained.

[0024] Furthermore, the mass concentration of the obtained pH self-adaptive deep defluorination composite coagulant for electronic industrial wastewater is 10 wt%.

[0025] The present invention also proposes a hierarchical defluorination treatment method for electronic industrial wastewater. Add the deep defluorination composite coagulant for electronic industrial wastewater or the deep defluorination composite coagulant for electronic industrial wastewater prepared according to the preparation method to the electronic industrial wastewater, adjust the pH of the electronic industrial wastewater to 6.5 ± 0.2, and achieve deep defluorination of the electronic industrial wastewater through primary or secondary hierarchical treatment;

[0026] The dosage of the composite coagulant in the electronic industrial wastewater is 200 - 1000 mg / L.

[0027] Furthermore, the pH of the electronic industrial wastewater is 7 - 9, and the concentration of fluoride ion (F - ) is < 10 mg / L.

[0028] Furthermore, the dosage of the composite coagulant in the electronic industrial wastewater is determined according to the pH of the wastewater and the concentration of F - in the wastewater, and the dosage of the composite coagulant in the electronic industrial wastewater is 200 - 1000 mg / L.

[0029] Furthermore, it specifically includes the following steps:

[0030] Add the composite coagulant to the electronic industrial wastewater, start the coagulation stirring program, add an anionic polyacrylamide solution (anionic PAM solution) after stirring and continue stirring. After standing and sedimenting, complete the separation of mud and water to achieve deep defluorination of the electronic industrial wastewater.

[0031] Even further, add the composite coagulant to the electronic industrial wastewater, and do not add or add a small amount of acid-base regulator to adjust the pH of the electronic industrial wastewater to 6.5 ± 0.2.

[0032] Even further, the mass concentration of the anionic polyacrylamide solution is 1‰, and the addition amount in the electronic industrial wastewater is 0.5 mg / L.

[0033] Even further, the primary or secondary hierarchical treatment defluorination treatment method for electronic industrial wastewater in the present invention includes primary defluorination or secondary defluorination. That is, the hierarchical treatment method includes the following two implementation manners:

[0034] (1) Primary defluorination: Achieve the standard of fluoride ion concentration through single addition of the composite coagulant;

[0035] (2) Secondary defluorination: After the primary defluorination, a composite coagulant is added again for enhanced treatment.

[0036] Among them, the primary defluorination means adding a composite coagulant once, which specifically includes the following steps:

[0037] S1. First, measure the pH value and the initial F - concentration of the electronic industrial wastewater to be treated;

[0038] S2. Depending on the initial wastewater pH value and the initial F - concentration, the proportion of aluminum sulfate and PAC in the composite coagulant can be appropriately adjusted to ensure that without adding or adding a small amount of acid-base regulator, the direct addition of the composite coagulant can maintain the pH of the wastewater within the optimal pH value range of 6.5 ± 0.2 and ensure that the effluent meets the standards;

[0039] S3. Start the coagulation stirring program. First, stir rapidly at 100 rpm for 5 min;

[0040] S4. Then add a certain amount of 1‰ (mass concentration) anionic PAM solution, and then stir slowly at 40 rpm for 10 min;

[0041] S5. Let it stand for sedimentation for 10 min;

[0042] S6. Measure the F - concentration of the coagulated effluent. The supernatant meets the standards and is discharged, realizing the deep defluorination of the electronic industrial wastewater.

[0043] For secondary defluorination, on the basis of primary defluorination, after standing for sedimentation, add the composite coagulant to the coagulated effluent again, which specifically includes the following steps:

[0044] S1. First, measure the pH value and the initial F - concentration of the electronic industrial wastewater to be treated;

[0045] S2. Depending on the initial wastewater pH value and the initial F - concentration, the proportion of aluminum sulfate and PAC in the composite coagulant can be appropriately adjusted to ensure that without adding or adding a small amount of acid-base regulator, the direct addition of the composite coagulant can maintain the pH of the wastewater within the optimal pH value range of 6.5 ± 0.2 and ensure that the F - concentration of the primary coagulated effluent decreases to a certain extent;;

[0046] S3. Start the coagulation stirring program. First, stir rapidly at 100 rpm for 5 min;

[0047] S4. Then add a certain amount of 1‰ anionic PAM solution, and then stir slowly at 40 rpm for 10 min;

[0048] S5, Let it stand and precipitate for 10 min;

[0049] S6, Measure the concentration of F and pH value of the effluent from the first-stage coagulation; - concentration and pH value;

[0050] S6, Add the composite coagulant for the second time, and repeat steps S3 - S5;

[0051] S7, Measure the concentration of F in the effluent from the second-stage coagulation; - The concentration of the supernatant meets the discharge standard, realizing the deep defluorination of electronic industrial wastewater.

[0052] Compared with the prior art, the present invention has the following advantages and technical effects:

[0053] (1) In the present invention, an inorganic small-molecule coagulant (aluminum sulfate) and an inorganic polymer coagulant (PAC) are compounded at a mass ratio of (1:3) - (3:1), breaking through the limitations of a single agent. Aluminum sulfate hydrolyzes and releases Al 3+ rapidly adsorbs fluoride ions, and PAC forms dense flocs through the bridging of polymer chains. The two work together to improve the defluorination efficiency. The dynamic balance between the strong hydrolysis of aluminum sulfate and the weak hydrolysis of PAC enables the composite coagulant to stabilize the pH at 6.5 ± 0.2 in wastewater with an initial pH = 7 - 9 without or with only a small amount of acid-base adjustment, significantly reducing the consumption of acid and base.

[0054] (2) In the composite coagulant of the present invention, aluminum sulfate is an inorganic small-molecule coagulant, and its main defluorination mechanism is complexation, ion exchange and adsorption; PAC is an inorganic polymer coagulant, and its defluorination mechanism is mainly ion exchange and adsorption. Mixing coagulants with different molecular weights can increase the collision frequency and aggregation efficiency. The larger molecular weight PAC can serve as a "bridging" point to connect multiple small-molecule aluminum sulfates to form a more complex flocculation network structure, which helps to capture fluoride ions, improve the overall flocculation efficiency and sedimentation performance.

[0055] (3) The composite coagulant of the present invention synergistically acts with the dynamic ratio adjustment mechanism and the staged dosing process, significantly improving the adaptability to water quality fluctuations. For different initial pH and fluoride ion concentrations, the ratio of aluminum sulfate to PAC (1:3 - 3:1) can be flexibly adjusted to adaptively maintain the optimal reaction pH range (6.5 ± 0.2) without or with a small amount of external acid-base adjustment. Through the first-stage / second-stage staged treatment process, the present invention realizes the deep removal of fluoride ions. Combining with the stable sedimentation characteristics of dense flocs, it effectively inhibits the secondary pollution of water quality caused by sludge back-dissolution and enhances the tolerance of the system to water quality fluctuations. This design breaks through the strict requirements of traditional processes for water quality stability, while ensuring that the effluent fluoride concentration stably meets the surface water class III / IV standards, significantly reducing the comprehensive chemical cost, and without relying on a complex external control system, simplifying the operation and management process. Brief Description of the Drawings

[0056] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0057] Figure 1 Shows the defluorination results after coagulation stirring treatment and 3 - minute static precipitation under different mass ratios of aluminum sulfate and PAC in Example 1 (3:1), Example 2 (1:3), Example 5 (1:1), Comparative Example 1 (1:0), and Comparative Example 2 (0:1) of the present invention;

[0058] Figure 2 Presents the photos of defluorination precipitation flocs after coagulation stirring treatment under different mass ratios of aluminum sulfate and PAC in Example 1 (3:1), Example 2 (1:3), Example 5 (1:1), Comparative Example 1 (1:0), and Comparative Example 2 (0:1) of the present invention;

[0059] Figure 3 Illustrates the F - concentration in the coagulated effluent of Example 2 (dosage of primary defluorination composite coagulant is 900 mg / L), Example 3 (dosage of secondary defluorination composite coagulant is 500 mg / L + 200 mg / L), Example 4 (dosage of secondary defluorination composite coagulant is 500 mg / L + 400 mg / L), and the F - concentration in the original electronic industrial wastewater. Detailed Description of the Invention

[0060] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0061] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0062] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0063] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0064] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0065] An embodiment of this invention provides a composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH self - adaptation, which is composed of an inorganic small - molecule coagulant and an inorganic polymer coagulant with a mass ratio of (1:3) - (3:1). The inorganic small - molecule coagulant is aluminum sulfate, and the inorganic polymer coagulant is polyaluminum chloride (PAC).

[0066] An embodiment of this invention also provides a preparation method of the composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH self - adaptation, comprising the following steps:

[0067] Weigh each raw material according to the mass ratio, dissolve aluminum sulfate in water and stir evenly, then add polyaluminum chloride, and after stirring evenly, obtain the composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH self - adaptation.

[0068] In a preferred embodiment of this invention, the mass concentration of the obtained composite coagulant is 10 wt%.

[0069] An embodiment of this invention also provides a hierarchical fluoride - removal treatment method for electronic industrial wastewater. Add the composite coagulant or the composite coagulant prepared according to the preparation method to the electronic industrial wastewater, and adjust the pH of the electronic industrial wastewater to 6.5 ± 0.2. Through primary treatment or secondary treatment, deep fluoride removal from the electronic industrial wastewater is achieved.

[0070] In a preferred embodiment of this invention, the pH of the electronic industrial wastewater is 7 - 9, and the F - concentration < 10 mg / L.

[0071] In a preferred embodiment of the present invention, the dosage of the composite coagulant in the electronic industrial wastewater is determined according to the pH of the wastewater and the F - concentration in the wastewater; more specifically, the dosage of the composite coagulant in the electronic industrial wastewater is 200 - 1000 mg / L. As a preference, the dosage of the composite coagulant in the electronic industrial wastewater is 700 - 900 mg / L. More specifically, the dosage of the composite coagulant in the electronic industrial wastewater is 900 mg / L (dosage for primary defluorination), or 700 - 900 mg / L (dosage for secondary defluorination).

[0072] In a preferred embodiment of the present invention, it specifically includes the following steps:

[0073] Add the composite coagulant into the electronic industrial wastewater, start the rapid coagulation stirring program, then add the anionic polyacrylamide solution (anionic PAM solution) to enter the slow stirring process. After standing and sedimenting, complete the separation of mud and water, and measure the F - concentration in the supernatant of the coagulation to achieve deep defluorination of the electronic industrial wastewater.

[0074] In a preferred embodiment of the present invention, when adding the composite coagulant into the electronic industrial wastewater, no or a small amount of acid-base regulator is added to adjust the pH of the electronic industrial wastewater to 6.5 ± 0.2.

[0075] In a preferred embodiment of the present invention, the mass concentration of the anionic polyacrylamide solution is 1‰, and the addition amount in the electronic industrial wastewater is 0.5 mg / L.

[0076] In a preferred embodiment of the present invention, the method for deep defluorination of electronic industrial wastewater includes primary defluorination or secondary defluorination.

[0077] Among them, primary defluorination means adding the composite coagulant once for mixing and sedimentation defluorination, which specifically includes the following steps:

[0078] S1. First, measure the pH value and the initial F - concentration of the electronic industrial wastewater to be treated;

[0079] S2. Depending on the initial wastewater pH value and the initial F - concentration, appropriately adjust the proportion of aluminum sulfate and PAC in the composite coagulant to ensure that without adding or adding a small amount of acid-base regulator, the direct addition of the composite coagulant can keep the pH of the wastewater within the range of 6.5 ± 0.2 and ensure that the effluent meets the standards;

[0080] S3. Start the coagulation stirring program, first stir rapidly at 100 rpm for 5 min;

[0081] At S4, add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then stir slowly at 40 rpm for 10 min;

[0082] At S5, let it stand for sedimentation for 10 min;

[0083] At S6, measure the F concentration in the coagulated effluent - The concentration, and the supernatant meets the discharge standard, realizing the deep defluorination of electronic industrial wastewater.

[0084] The secondary defluorination is based on the primary defluorination, and a composite coagulant is added again to the primary coagulated effluent for secondary deep defluorination, which specifically includes the following steps:

[0085] At S1, first measure the pH value and the initial F concentration of the electronic industrial wastewater to be treated; - concentration;

[0086] At S2, depending on the initial wastewater pH value and the initial F concentration, the proportion of aluminum sulfate and PAC in the composite coagulant can be appropriately adjusted to ensure that without adding or adding less acid-base regulator, the direct addition of the composite coagulant can maintain the pH of the wastewater within the optimal range of 6.5 ± 0.2, and ensure that the F concentration in the primary coagulated effluent - has a certain degree of decrease; - concentration;

[0087] At S3, start the coagulation stirring program. First, stir quickly at 100 rpm for 5 min;

[0088] At S4, then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then stir slowly at 40 rpm for 10 min;

[0089] At S5, let it stand for sedimentation for 10 min;

[0090] At S6, measure the F concentration and pH value of the primary coagulated effluent; - concentration and pH value;

[0091] At S7, add the composite coagulant for the second time, and repeat steps S3 - S5;

[0092] At S8, measure the F concentration of the secondary coagulated effluent - The concentration, and the supernatant meets the discharge standard, realizing the deep defluorination of electronic industrial wastewater.

[0093] In the embodiment of the present invention, the F discharge standard for Class III water in the surface water environmental quality standard is: - F concentration ≤ 1.0 mg / L, and the F discharge standard for Class IV water in the surface water environmental quality standard is: - F concentration ≤ 1.5 mg / L. - F concentration ≤ 1.5 mg / L. - concentration ≤ 1.5 mg / L.

[0094] The raw materials used in the embodiments of the present invention are all commercially available and purchased.

[0095] The technical solutions of the present invention are further described below through embodiments.

[0096] Example 1

[0097] Take 1000 mL of a certain electronic industrial wastewater. After measurement, the initial pH value of the wastewater is 7.71, and the initial F - concentration is 5.92 mg / L.

[0098] A hierarchical defluorination treatment method for electronic industrial wastewater, using primary defluorination, specifically includes the following steps:

[0099] S1, Weigh aluminum sulfate and PAC according to a mass ratio of 3:1. Dissolve the aluminum sulfate in water and stir with a magnetic stirrer for 10 min; then add PAC and stir with a magnetic stirrer for 20 min. After stirring evenly, a composite coagulant with a mass concentration of 10 wt% is obtained;

[0100] S2, Add the above composite coagulant to the electronic industrial wastewater at a dosage of 900 mg / L. The pH drops to 4.94. Add 30 wt% sodium hydroxide solution to adjust the pH of the mixed system to 6.5 ± 0.2;

[0101] S3, Rapidly stir the above mixed system at 100 rpm for 5 min, then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir at 40 rpm for 10 min; After standing and precipitating for 10 min, measure the F - concentration in the coagulated effluent.

[0102] The results show that the F - concentration in the supernatant effluent in Example 1 of the present invention is reduced to 0.98 mg / L, meeting the effluent standard of Class III water in the surface water environmental quality standard.

[0103] Comparative Example 1

[0104] Take 1000 mL of a certain electronic industrial wastewater. After measurement, the initial pH value of the wastewater is 7.71, and the initial F - concentration is 5.92 mg / L.

[0105] A hierarchical defluorination treatment method for electronic industrial wastewater, using primary defluorination, specifically includes the following steps:

[0106] S1, Dissolve aluminum sulfate in water and stir with a magnetic stirrer for 10 min; After stirring evenly, an aluminum sulfate solution with a mass concentration of 10 wt% is obtained;

[0107] S2. Add an aluminum sulfate solution with a mass concentration of 10 wt% to the electronic industrial wastewater at a dosage of 900 mg / L. The pH drops to 4.57. Then add a 30 wt% sodium hydroxide solution to adjust the pH of the mixed system to 6.5 ± 0.2.

[0108] S3. Rapidly stir the above mixed solution at 100 rpm for 5 min, then add a 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir at 40 rpm for 10 min. After standing and precipitating for 10 min, measure the F concentration of the coagulated effluent. - Concentration.

[0109] The results show that the F concentration of the supernatant effluent in Comparative Example 1 of the present invention is 0.88 mg / L, meeting the effluent standard of Class III water in the Surface Water Environment Quality Standard. - Concentration is 0.88 mg / L, meeting the effluent standard of Class III water in the Surface Water Environment Quality Standard.

[0110] Under the effluent standard of Class III water in the Surface Water Environment Quality Standard, compared with the defluorination using aluminum sulfate at the same dosing concentration (Comparative Example 1), the caustic soda consumption of the composite coagulant in the technical solution of Example 1 decreases by 38.46%.

[0111] Example 2

[0112] Take 1000 mL of a certain electronic industrial wastewater. After measurement, the initial pH value of the wastewater is 7.71, and the initial F concentration is 5.92 mg / L. - Concentration is 5.92 mg / L.

[0113] A hierarchical defluorination treatment method for electronic industrial wastewater, adopting primary defluorination, specifically including the following steps:

[0114] S1. Weigh aluminum sulfate and PAC according to a mass ratio of 1:3. Dissolve the aluminum sulfate in water and stir with a magnetic stirrer for 10 min. Then add PAC and stir with a magnetic stirrer for 20 min to prepare a composite coagulant with a mass concentration of 10 wt%.

[0115] S2. Add the above composite coagulant to the electronic industrial wastewater at a dosage of 900 mg / L. The pH of the mixed system is 6.4, and there is no need to adjust the pH.

[0116] S3. Rapidly stir the above mixed system at 100 rpm for 5 min, then add a 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir at 40 rpm for 10 min. After standing and precipitating for 10 min, measure the F concentration of the coagulated effluent. - Concentration.

[0117] The results show that the F concentration of the supernatant effluent in Example 2 of the present invention -The concentration is reduced to 1.23 mg / L, meeting the effluent standard of Class IV surface water environmental quality standard. During this process, the sludge production from coagulation and sedimentation in step S3 is 1.63 kg / t.

[0118] Comparative Example 2

[0119] Take 1000 mL of a certain electronic industrial wastewater. After measurement, the initial pH value of the wastewater is 7.71, and the initial F - ion concentration is 5.92 mg / L.

[0120] A hierarchical defluorination treatment method for electronic industrial wastewater, using primary defluorination, specifically including the following steps:

[0121] S1, Dissolve a certain amount of PAC in water and stir with a magnetic stirrer for 10 min to prepare a PAC solution with a mass concentration of 10 wt%.

[0122] S2, Add the 10 wt% PAC solution to the electronic industrial wastewater at a dosage of 900 mg / L. The pH of the mixed system is 6.96. Add 10 wt% sulfuric acid solution to adjust the pH of the mixed system to 6.5 ± 0.2.

[0123] S3, Rapidly stir the above mixed solution at 100 rpm for 5 min, then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir at 40 rpm for 10 min; After standing and sedimenting for 10 min, measure the F - ion concentration in the coagulation effluent.

[0124] The results show that the F - concentration in the supernatant effluent of Comparative Example 2 of the present invention is 1.43 mg / L, meeting the effluent standard of Class IV surface water environmental quality standard. During this process, the sludge production from coagulation and sedimentation in step S3 is 1.93 kg / t.

[0125] By comparing Example 2 and Comparative Example 2, it can be seen that under the effluent standard of Class IV surface water environmental quality standard and at the same chemical dosage concentration, compared with PAC defluorination (Comparative Example 2) in Example 2, the acid-base consumption in the method of Example 2 is 0, and the sludge production is reduced by 6%.

[0126] Example 3

[0127] Take 1000 mL of a certain electronic industrial wastewater. After measurement, the initial pH value of the wastewater is 7.65, and the initial F - ion concentration is 5.42 mg / L.

[0128] A hierarchical defluorination treatment method for electronic industrial wastewater, using secondary defluorination, specifically including the following steps:

[0129] S1. Weigh aluminum sulfate and PAC according to a mass ratio of 1:3. Dissolve the aluminum sulfate in water and stir it with a magnetic stirrer for 10 minutes. Then add PAC and stir it with a magnetic stirrer for 20 minutes to prepare a composite coagulant with a mass concentration of 10 wt%.

[0130] S2. Add the above composite coagulant to the electronic industrial wastewater at a dosage of 500 mg / L. The pH of the mixed system drops to 6.7, and there is no need to further consume acid and alkali agents.

[0131] S3. Rapidly stir the above mixed solution at 100 rpm for 5 minutes. Then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir it at 40 rpm for 10 minutes. After standing and sedimenting for 10 minutes, the F concentration in the supernatant after the first-stage defluorination - decreases to 1.80 mg / L.

[0132] S4. Perform secondary defluorination on the supernatant after the first-stage defluorination. The dosage concentration of the composite coagulant is 200 mg / L, and the pH of the mixed system is 6.45. There is no need to further consume acid and alkali agents.

[0133] S5. Rapidly stir it at 100 rpm for 5 minutes. Then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir it at 40 rpm for 10 minutes. After standing and sedimenting for 10 minutes, the F concentration in the supernatant - decreases to 1.03 mg / L, approaching the Class III water standard of the surface water environmental quality standard.

[0134] Example 4

[0135] Take 1000 mL of a certain electronic industrial wastewater. After measurement, the initial pH value of the wastewater is 7.65, and the initial F - concentration is 5.42 mg / L.

[0136] A hierarchical defluorination treatment method for electronic industrial wastewater, which adopts secondary defluorination, specifically includes the following steps:

[0137] S1. Weigh aluminum sulfate and PAC according to a mass ratio of 1:3. Dissolve the aluminum sulfate in water and stir it with a magnetic stirrer for 10 minutes. Then add PAC and stir it with a magnetic stirrer for 20 minutes to prepare a composite coagulant with a mass concentration of 10 wt%.

[0138] S2. Add the above composite coagulant to the electronic industrial wastewater at a dosage of 500 mg / L. The pH of the mixed system drops to 6.7, and there is no need to further consume acid and alkali agents.

[0139] S3. Rapidly stir the above mixed solution at 100 rpm for 5 min, then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir at 40 rpm for 10 min; after standing and sedimenting for 10 min, the supernatant water after primary defluorination has an F - concentration reduced to 1.80 mg / L;

[0140] S4. Perform secondary defluorination on the supernatant water after primary defluorination. The dosing concentration of the composite coagulant is 400 mg / L, and the pH of the mixed system is 6.45, without further consumption of acid and alkali agents;

[0141] S5. Rapidly stir at 100 rpm for 5 min; then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir at 40 rpm for 10 min; after standing and sedimenting for 10 min, the supernatant water has an F - concentration reduced to 0.7 mg / L, meeting the water quality standard of Class III surface water environment quality standard.

[0142] Example 5

[0143] Take 1000 mL of a certain electronic industrial wastewater. After measurement, the initial pH value of the wastewater is 7.71, and the initial F - concentration is 5.92 mg / L.

[0144] A hierarchical defluorination treatment method for electronic industrial wastewater, using primary defluorination, specifically including the following steps:

[0145] S1. Weigh aluminum sulfate and PAC according to a mass ratio of 1:1. Dissolve aluminum sulfate in water and stir with a magnetic stirrer for 10 min; then add PAC and stir with a magnetic stirrer for 20 min to prepare a composite coagulant with a mass concentration of 10 wt%;

[0146] S2. Add the above composite coagulant to the electronic industrial wastewater at a dosage of 900 mg / L. The pH value of the wastewater drops to 5.83. Add 30 wt% sodium hydroxide solution to adjust the pH of the mixed system to 6.5 ± 0.2;

[0147] S3. Rapidly stir the above mixed solution at 100 rpm for 5 min, then add 1‰ anionic PAM solution at a dosage of 0.5 mg / L, and then slowly stir at 40 rpm for 10 min; after standing and sedimenting for 10 min, perform mud-water separation and measure the F - concentration in the coagulated effluent.

[0148] The results show that in Example 5 of the present invention, the F - concentration in the supernatant water is reduced to 1.22 mg / L, meeting the effluent standard of Class IV water in the surface water environment quality standard.

[0149] According to the methods in Example 1 (3:1), Example 2 (1:3), Example 5 (1:1), Comparative Example 1 (1:0), and Comparative Example 2 (0:1) of the present invention, different mass ratios of aluminum sulfate and PAC were set, and coagulation stirring treatment was carried out under different mixing ratio conditions. The defluorination results after standing and precipitating for 3 min are shown in Figure 1 , and the photos of the defluorination precipitate flocs after standing and precipitating for 10 min are shown in Figure 2 .

[0150] From Figure 1 it can be seen that at the initial stage of the slow stirring end, the flocs in the coagulation systems with 50% and 75% PAC showed excellent sedimentation effects. Among them, the group with aluminum sulfate:PAC of 1:3 (Example 2), that is, when the PAC ratio was 75%, had the best effect; from Figure 2 it can be seen that the precipitate floc structures generated by the single aluminum sulfate group and the single PAC group were relatively loose; for the composite coagulant, with the increase of the PAC component ratio, obvious sediment-water separation phenomenon occurred in the system, and the precipitate flocs became more and more dense, and the group with aluminum sulfate:PAC of 1:3 (Example 2) had the best effect.

[0151] The F - concentration in the effluent of coagulation in Example 2 (the dosage of the primary defluorination composite coagulant was 900 mg / L), Example 3 (the dosage of the secondary defluorination composite coagulant was 500 mg / L + 200 mg / L), Example 4 (the dosage of the secondary defluorination composite coagulant was 500 mg / L + 400 mg / L), and the F - concentration in the original electronic industrial wastewater are shown in Figure 3 , and it can be seen that under the same total dosage of 900 mg / L, the primary defluorination and secondary defluorination of the composite coagulant prepared by the present invention can ensure that the electronic industrial wastewater is deeply defluorinated to meet the water quality standards of Class IV and Class III of the surface water environment quality standard respectively.

[0152] Comparative Example 3

[0153] Same as Example 1, the difference is only that in step S1, aluminum sulfate and PAC were weighed at a mass ratio of 5:1, and the remaining steps were the same as those in Example 1.

[0154] The results showed that the initial pH of the mixed system decreased to 4.75, and 30 wt% sodium hydroxide solution was added to adjust it to 6.5 ± 0.2; the F- concentration in the supernatant effluent decreased to 0.93 mg / L, and the floc density was slightly lower than that in Example 1. The reason for the analysis is that the proportion of aluminum sulfate in the 5:1 ratio increased, and the release amount of Al 3+ increased, resulting in a further decrease in the pH of the mixed system. Although the composite coagulant under this ratio could generate more Al(OH)3 colloids to adsorb F - , making the F -The concentration is slightly lower than that in Example 1, but the overall advantage is not significant. In addition, the too low proportion of PAC makes the floc structure sensitive to water quality fluctuations.

[0155] Comparative Example 4

[0156] Same as Example 2, except that in step S1, aluminum sulfate and PAC are weighed at a mass ratio of 1:5, and the remaining steps are the same as those in Example 2.

[0157] The results show that the initial pH of the mixed system only drops to 7.2 (the original wastewater pH = 7.71), the F- concentration in the supernatant is 1.78 mg / L, which does not meet the Class IV surface water standard, and the sludge volume increases to 1.82 kg / t.

[0158] The reason for the analysis is that the too high proportion of PAC leads to a significant weakening of the hydrolysis ability of the composite coagulant, and the pH only drops to 7.2 after mixing. The insufficient proportion of aluminum sulfate results in limited release of Al 3+ and it is impossible to form sufficient Al(OH)3 to adsorb fluoride ions; although the excessive PAC enhances the bridging effect, due to the lack of synergy of small molecule coagulants, the floc network is sparse, and finally the defluorination efficiency is inferior to that in Example 2.

[0159] Comparative Example 5

[0160] Same as Example 1, except that in step S2, the pH of the mixed system is adjusted to 9, and the remaining steps are the same as those in Example 1.

[0161] The results show that after the addition of the composite coagulant, the pH of the mixed system drops significantly from 9 to 5.8, and the F - concentration in the supernatant decreases to 1.0 mg / L, meeting the Class III surface water standard (≤1.0 mg / L). The reason for the analysis is that the proportion of aluminum sulfate in the composite coagulant is high, and its strong hydrolysis releases a large amount of H + (Al 3+ +3H2O→Al(OH)3+3H + ), even if the initial pH = 9, it can still neutralize OH + through H - and quickly reduce the system pH to 5.8, approaching the optimal reaction window.

[0162] To sum up, in Example 2 (1:3 ratio), when the initial pH = 7.71, the pH automatically drops to 6.4 after addition, without the need for acid-base adjustment, and the F - in the effluent reaches 1.23 mg / L (Class IV standard);

[0163] In Comparative Example 4 (1:5 ratio), due to the too high proportion of PAC, the pH only drops to 7.2, resulting in poor defluorination effect, which reflects the importance of the critical control of the drug ratio on pH self-adaptation;

[0164] Example 4: Through secondary dosing (500 + 400 mg / L), the final pH was stabilized at 6.45, and the effluent F - was reduced to 0.7 mg / L (Class III standard), verifying the feasibility of staged adaptive regulation.

[0165] Therefore, the composite coagulant prepared by the present invention realizes pH adaptive regulation through two-component hydrolysis balance, complementary aluminum salt forms, dynamic ratio adjustment and sludge structure optimization, significantly reduces the consumption of external acids and alkalis, and at the same time meets the requirements of deep defluorination.

[0166] The above is only the preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the technical field of the present application within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH adaptability, characterized in that, It is composed of an inorganic small molecule coagulant and an inorganic polymer coagulant with a mass ratio of (1:3) to (3:1). The inorganic small molecule coagulant is aluminum sulfate, and the inorganic polymer coagulant is polyaluminum chloride.

2. The preparation method of the composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH self - adaptation according to claim 1, characterized in that, It includes the following steps: Weigh each raw material according to the mass ratio, dissolve aluminum sulfate in water and stir evenly, then add polyaluminum chloride, and after stirring evenly, obtain the composite coagulant for deep fluoride removal from electronic industrial wastewater based on pH self - adaptation.

3. A hierarchical defluorination treatment method for electronic industrial wastewater, characterized in that, Add the composite coagulant for deep fluoride removal from electronic industrial wastewater described in claim 1 or the composite coagulant for deep fluoride removal from electronic industrial wastewater prepared by the preparation method described in claim 2 into the electronic industrial wastewater, adjust the pH of the electronic industrial wastewater to 6.5 ± 0.2, and through primary treatment or secondary treatment, achieve deep fluoride removal from the electronic industrial wastewater. The dosage of the composite coagulant in the electronic industrial wastewater is 200 - 1000 mg / L.

4. The hierarchical defluorination treatment method for electronic industrial wastewater according to claim 3, wherein, The pH of the electronic industrial wastewater is 7 - 9, and the fluoride ion concentration < 10 mg / L.

5. The hierarchical defluorination treatment method for electronic industrial wastewater according to claim 3, characterized in that, The specific primary treatment includes the following steps: Measure the pH value and initial fluoride ion concentration of the electronic industrial wastewater to be treated, add the composite coagulant for deep fluoride removal from electronic industrial wastewater into the electronic industrial wastewater, adjust the pH of the electronic industrial wastewater to 6.5 ± 0.2, start the coagulation stirring program, after stirring, add an anionic polyacrylamide solution and continue stirring, and after standing and sedimenting, complete the separation of mud and water to achieve deep fluoride removal from the electronic industrial wastewater.

6. The hierarchical defluorination treatment method for electronic industrial wastewater according to claim 5, characterized in that, The mass concentration of the anionic polyacrylamide solution is 1‰.

7. The hierarchical defluorination treatment method for electronic industrial wastewater according to claim 3, characterized in that, The specific secondary treatment includes the following steps: Measure the pH value and initial fluoride ion concentration of the electronic industrial wastewater to be treated, add the composite coagulant for deep fluoride removal from electronic industrial wastewater into the electronic industrial wastewater, adjust the pH of the electronic industrial wastewater to 6.5 ± 0.2, start the coagulation stirring program, after stirring, add an anionic polyacrylamide solution and continue stirring, separate the mud and water after standing and sedimenting, add the composite coagulant again, and repeat the above operations to achieve deep fluoride removal from the electronic industrial wastewater.

8. The hierarchical defluorination treatment method for electronic industrial wastewater according to claim 7, characterized in that, The mass concentration of the anionic polyacrylamide solution is 1‰.

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